Travel advice?

My plans for the 29th-1st have probably fallen through, so I need backup plans. I'll arrive in London on the morning of the 29th and had planned to go to the Victoria and Albert museum for the day. But after that I currently have nothing until I go to Paris on the afternoon of the 1st.

Of course, I could find a hostel in London, there's certainly plenty to do there. But is there any other place in southern England you would recommend? I like natural history, botany and birdwatching, hiking, and history (especially 18th century). Or if you live in southern England and would like to meet up, let me know.